1. Field of the Invention
The present invention relates to a spindle motor and a disk drive apparatus.
2. Description of the Related Art
Spindle motors arranged to rotate disks are installed in hard disk drive apparatuses and optical disk drive apparatuses. Such a spindle motor includes a stationary portion fixed to a housing of the apparatus, and a rotating portion arranged to rotate while supporting the disk(s). While the spindle motor is running, a torque centered on a central axis is produced by interaction of magnetic flux generated between the stationary portion and the rotating portion, so that the rotating portion is able to rotate with respect to the stationary portion. A known spindle motor is described, for example, in JP-A 2006-331558.
A so-called fluid dynamic bearing is used as a bearing of the spindle motor described in JP-A 2006-331558. The fluid dynamic bearing includes a stationary bearing portion, a rotatable bearing portion, and a lubricating fluid. A gap between the stationary bearing portion and the rotatable bearing portion is filled with the lubricating fluid. The rotating portion is supported by the fluid dynamic bearing to be rotatable with respect to the stationary portion.
If the fluid dynamic bearing as described above is used for a long period of time, the lubricating fluid in the fluid dynamic bearing gradually evaporates. If the amount of the lubricating fluid in the fluid dynamic bearing decreases, the rotatable bearing portion may become unable to rotate, or the rotatable bearing portion may come to rotate while being rubbed against the stationary bearing portion.
Accordingly, a structure which contributes to preventing evaporation of the lubricating fluid is demanded of a fluid dynamic bearing apparatus.